Method for inductively heating an elongated, slotted workpiece

ABSTRACT

A method and apparatus for inductively heating an elongated slotted tube preparatory to subsequent forming of said slotted tube comprising providing an inductor having a pair of parallel spaced apart heating conductor legs having a length at least as long as the length of the slot. The slotted tube is positioned between the conductor legs so that the side walls of the slot are positioned immediately adjacent and parallel to one of the legs. The inductor is then conventionally energized as the tube is rotated about its longitudinal axis to effect the desired heating.

I United States Patent 1191 [111 3,800,115 Cachat 51 Mar. 26, 1974METHOD FOR INDUCTIVELY HEATING 2,930,603 3/1960 Voss et a1 266/4 E ANELONGATED, SLOTTED WORKPIECE 3,441,701 4/1969 Seulen et a1.. 219/1043 v2,541,124 2/1951 Strickland 219/1057 [75] ln en o J n F Cachat,Cleveland, Ohio 3,336,459 8/1967 Seulen et a1. 219/1043 [73] As signee:Parker-Ohio Industries, Inc.,

Cleveland, Ohio Primary Examiner-Bruce A. Reynolds Filed Dec 8 1972Attorney, Agent, or Firm-Meyer, Tilberry & Body 21 A 1. N 313,505 1 pp 057 ABSTRACT Related US. Application Data [62] Division of Ser No 177 963S6 t 7 1971 A method and apparatus for 1nduct1vely heatmg an abandoned pelongated slotted tube preparatory to subsequent forming of said slottedtube comprising providing an 52 us. 01. 219/1043 219/10 57 inductorhaving a Pair of Parallel Spaced heating [51] in. CL H05b 6 conductorlegs having a length at least as long as the [58] Field of l 43 1O 57length of the slot. The slotted tube is positioned bed tween theconductor legs so that the side walls of the slot are positionedimmediately adjacent and parallel [56] References Cited to one of thelegs. The inductor is then conventionally energized as the tube isrotated about its longitudinal UNITED STATES PATENTS axis to effect thedesired heating. 3,483,346 12/1969 Seulen et a1. 219/1043 3,623,12811/1971 Seulen et a1. 219/1043 1 Claim, 3 Drawing Figures mamanmzs m43300.1 15

I NVEN'TOR. JOHN F. CAC HAT Mew, 7M 2 80d ATTORNEYS This is a divisionof application Ser. No. 177,963 filed Sept. 7, 1971, now abandoned.

This application pertains to the art of induction heating and moreparticularly to a method and apparatus for inductively heating anelongated slotted workpiece.

The invention is particularly applicable to inductively heatingelongated slotted tubes which are to be subsequently formed at theslotted area and will be described with particular reference thereto;however, it will be appreciated that the invention has broaderapplications and may be employed in any instance where elongatedworkpieces. having at least one aperture area therein are desired to beuniformly heated over at least the aperture area therein.

In induction heating it is known to pass elongated tubes through amulti-turn induction heating coil to effeet the desired heating. Thistype of apparatus and method are satisfactory for tubes and shafts whichhave a continuous peripheral surface; however, they are unsatisfactorywhen the workpieces being heated include a slotted or other recess areatherein. The difficulty encountered is that in using a multi-turn coilto effect induction heating, the induced current flow is generallyaround the workpiece in a direction normal to the workpiece longitudinalaxis. However, the induced current is unable to flow in this desiredpath along the slotted area as there is no workpiece area there throughwhich it may travel. Therefore, the current seeks other paths throughwhich to flow, such as for example, along the sides and around the endsof the slot. This interruption and alteration of the induced currentflow has the effect of establishing cold spots along the workpiece atthe slotted area. These spots are particularly undesirable when theworkpiece is to be formed subsequent to heating.

The present invention contemplates a new method and apparatus whichovercomes the above referred problems and provides a new method andapparatus for inductively heating elongated slotted tubes which iseconomical to employ, provides uniform heating over at least the slottedarea and is readily adaptable for use with other elongated workpieceshaving slotted or other apertures therein.

In accordance with the present invention there is provided a method ofheating an elongated workpiece having first and second terminal endportions and an intermediate portion including an aperture therethrough.The method comprises the steps of positioning the workpiece between apair of parallel spaced apart electrically interconnected heatingconductors such that at least said intermediate portion is in aninductive coupling relationship therewith; selectively energizing theheating conductors by passing an electrical current therethrough; and,rotating said workpiece abouts its longitudinal axis at least duringsaid energizing to effect heating of the entire of at least saidintermediate portion.

In accordance with another aspect of the present invention, there isprovided an induction heating apparatus for heating an elongatedworkpiece having terminal end portions and an intermediate portionincluding an aperture therethrough. The apparatus comprises an inductorhaving two elongated spaced apart parallel heating conductors definingan elongated heating zone therebetween, the heating conductors having alength at least as long as the intermediate portion. The apparatusfurther includes means for electrically interconnecting the heatingconductors and means for selectively supplying an electrical currentflow through the heating conductors. Means are provided for locating theworkpiece in a heating zone with at least the inter-' mediate portion inan inductive coupling relationship with the heating conductors.

In accordance with a limited aspect of the present invention, theworkpiece is rotated about its longitudinal axis by the locating meansduring heating.

The principal object of the present invention is the provision of amethod and apparatus for inductively heating elongated workpieces havingan aperture extending therethrough which provides for efficientinduction heating.

Another object of the present invention is the provision of a method andapparatus for inductively heating elongated workpieces having anaperture extending therethrough which are readily adaptable toworkpieces having any cross sectional configuration.

Still another object of the present invention is the provision of amethod and apparatus for inductively heating the elongated workpieceshaving an aperture extending therethrough which are economical toemploy.

The invention may take physical form in certain parts and arrangementsof parts, a preferred embodiment of which will be described in detail inthis specification and illustrated in the accompanying drawings whichform a part hereof and wherein:

FIG. 1 is a perspective view of the apparatus employing the concepts ofthe subject invention;

FIG. 2 is a plan view of the apparatus in FIG. 1 and showing anelongated slotted workpiece in an operative relationship therewith; and

FIG. 3 is a cross sectional in FIG. 2.

Referring now to the drawings wherein the showings are for the purposesof illustrating the preferred embodiment of the invention only and notfor purposes of limiting same, the Figures show inductive heatingapparatus A and elongated slot workpiece B.

In the preferred embodiment, the workpiece is an elongated piece of thinwalled steel tubing 10 having end portions 12,14. Wall 16 may be of anydesired thickness in order that the workpiece may be used for aparticular desired purpose. Disposed to extend longitudinally alongtubing 10 is an elongated slot 18 having side wall portions 20,22 andradiused end wall portions 24,26 although the invention may be used witha workpiece having any shape aperture therein. In accordance with theconcepts of the subject invention, it is desired to uniformly heat atleast the side wall portions and radiused end wall portions to anelevated temperature of approximately 2,000 F. in order that tubing 10may be formed into a final desired configuration.

The induction heating apparatus A employed to perform this desiredheating is comprised of a base portion 50 and conductor portion 52. Thebase portion is comprised of a pair of base plates 54,56 constructedfrom an electrically conductive material such as copper and are disposedin any convenient manner with an insulating material 58 therebetween.These base plates further include mounting holes 60 therethrough tofacilitate view taken along lines 3-3 rigidly affixing induction heatingapparatus A in a desired position. Further included are a pair ofupstanding conductor legs 62,64 mounted to plates 54,56 respectively ina known fashion. Legs 62,64 are constructed from an electricallyconductive material which, in the preferred embodiment, comprises ahollow rectangular copper tubing. To provide rigidity of constructionbetween the upstanding conductor legs and the base plates, wedge-shapedsupports 65 are provided to extend between them in a known manner. Itshould be noted that insulating material 58 also extends betweenupstanding conductors legs 62,64 and their respective wedge-shapedsupports 65. This insulating material is merely to prevent shortcircuiting of the induction heating apparatus as will hereinafter becomeapparent.

Affixed to legs 62,64 are the conductors which make up the actualheating zone and which comprise a generally normally extending heatingconductor leg 70 and a second cross-over leg 72. Leg 72 is affixed toupstanding leg 64 and is generally parallel to and identical inshapewith cross-over leg 68. Further, legs 66,70 are generally parallel toeach other and are each at least as long as the length of slot 18. Legs62,66,68,70,72 and 64 establish a circuit adapted to carry a currentflow to effect induction heating as will hereinafter become moreapparent and are, in the preferred embodiment, constructed fromrectangular copper tubing.

Disposed in a side-by-side relationship longitudinally along legs 66,70are a plurality of thin laminations 74 as is known in the inductiveheating art and which may be stamped from thin sheet steel. Eachlamination is generally U-shaped and includes base 75 and a pair ofoutwardly extending legs 76 which closely embrace the top, bottom andouter walls of the associated heating conductors 66,70. A cooling fluidinlet 80 disposed in base plate 54 to extend therethrough to the hollowcentral area of upstanding leg 62 and a fluid outlet 82 is disposed inbase plate 56 to extend outwardly from the hollow central portion ofupstanding leg 64. In this manner, and as known in the art, acoolingfluid such as water may be continuously pumped through theconductor legs to carry away some of the heat generated during theinductor operation. A high frequency electrical generator generallydesignated 90 is disposed across base plates 54,56 in order to supply acurrent flow through theconductor legs. Thus, insulation material 58assures that no shorting between base plates 54,56; upstanding legs62,64; or, wedge-shaped support 65 will occur during operation.

In using the above described induction heating apparatus, it isnecessary to mount the apparatus via mounting holes 60 disposed in baseplates 54,56. It is most desirable that when installed, heatingconductors 66,70 are disposed in a generally horizontal direction. Tubelocating and supporting means generally designated 92 in FIG. 2 areutilized to maintain tubing in a generally horizontal position betweenand in an inductive coupling relationship with inductors 66,70. Thistube locating and supporting means may comprise any convenient meanssuch as, for example, a standard chuck arrangement and further, in orderto assure that the tubing will be rigidly located, a positioning means92 could be utilized at each end of the tubing. In addition, thelocating and positioning means rotate so as to be able to continuouslyrotate the workpiece about its longitudinal axis. Any convenient powermeans may be used to effect this desired rotation of the locating means.

As shown in FIGS. 2 and 3, tubing 10 is positioned so that slot 18 iscoextensive with conductors 66,68 and rotated by locating means 92 indirection a (FIG. 3). When electrical supply generator 90 is energized,there is effected a current flow through the conductor legs andlaminations 74 associated with heating conductor legs 66,70 as is knownin the induction heating art. The current flow, particularly throughheating legs 66,70 and associated lamination 74, causes an inducedcurrent to longitudinally flow in side wall portions 22,20 respectivelyin the opposite direction. As the current flow in the inductor isreversed, the direction of flow of the induced current is also reversedto effect induction heating of these portions as is known.

As the induced current flow is longitudinal of the slot, there is nocurrent flow interruption or alteration during heating thus permittingconstant and even heating of at least the slotted area. The workpiecerotation assures even heating of the entire slot area. Once the desiredtemperature, approximately 2,000 F., has been reached, electrical supplygenerator may be de-energized and the workpiece removed from locatingand supporting means 92-for further processing and a new tube 10installed for heating as hereinabove described. If it is desired to heatend portions 12,14 in addition to side wall portions 20,22 the length ofconductors 66,70 need only be extended as desired or conventionalmulti-turn coils may be employed.

The invention has now been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon the reading and understanding of this specification. It ismy intention to include all such modifications and alterations insofaras they come within the scope of the appended claims or the equivalentsthereof.

Having thus described my invention, I now claim:

1. A method of uniformly heating the metal forming an axial portion ofan elongated workpiece to define to subsequent forming of said metal,said axial portion forming only a part of said elongated workpiece andincluding an elongated axially extending slot extending diametricallythrough said workpiece todefine two spaced apart, elongated ribs, saidheating method comprising the steps of:

a. locating said workpiece to extend along a given axis;

b. providing a single turn inductor having two spaced, generallyparallel conductors each having a length generally matching the lengthof said axial portion of said workpiece;

c. locating said inductor with said conductors parallel to said axis,coextensive with said axial portion and spaced outwardly from said tworibs a distance to cause magnetic coupling between said conductors andthe metal forming said axial portion of said workpiece;

d. energizing said inductor until at least said ribs are heateduniformly and evenly to a subsequent processing temperature;

e. rotating said workpiece about said given axis; and,

f. forming said heated axial portion of said workpiece.

UNITED STATES PATENT- OFFICE CERTIFICATE OF CORRECTION Patent No. 0,115Dsted March 1-974 Inventor(s) JOhn F. Cachat It is certi fied that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Assignee should read Psrk-Ohio Industries, Inc.

Signed and sealed this 26th day of November 1974.

( EAL) Attest:

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents UsC OMM-DC 6O376-Pfl9 us. covnuunlr PRINTING OFFICE nu0-368-334.

FORM PO-lOSO (10-69) UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,300,115 Dated March 2'6, 1974 Inventor(s) John FCachat It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Assignee should read ---Park-0hio Industries, Inc.

' Signed and sealed this 26th day of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. M ARSPMHIL DANN Attesting Officer Qontnissionerof Patents FORM P0405) (10-59) 1 uscoMM-oc 60378-P69 9 ".5. GQVERNHENTPRINTING OFFICE l9, 0-356-331.

1. A method of uniformly heating the metal forming an axial portion ofan elongated workpiece to define to subsequent forming of said metal,said axial portion forming only a part of said elongated workpiece andincluding an elongated axially extending slot extending diametricallythrough said workpiece todefine two spaced apart, elongated ribs, saidheating method comprising the steps of: a. locating said workpiece toextend along a given axis; b. providing a single turn inductor havingtwo spaced, generally parallel conductors each having a length generallymatching the length of said axial portion of said workpiece; c. locatingsaid inductor with said conductors parallel to said axis, coextensivewith said axial portion and spaced outwardly from said two ribs adistance to cause magnetic coupling between said conductors and themetal forming said axial portion of said workpiece; d. energizing saidinductor until at least said ribs are heated uniformly and evenly to asubsequent processing temperature; e. rotating said workpiece about saidgiven axis; and, f. forming said heated axial portion of said workpiece.